quick leak down question

I rotated the cams so the valves should be closed all the way on #4 cylinder. Checked clearance and its at .018 so no lobes are contacting either intake or exhaust valves. Took the plug out and put pressure thru plug hole and I have air leaking through the carb. Seems to me that I have a bent valve? 

Do you have a reason to expect one is bent?

Might just be carbon deposit on the valve or the seat.

You may know all of this already and it might not apply in any way.  That said, in case you didn't know...

The valves lose clearance with mileage as the valve heads pound into the seats, and at some point all the clearance will be gone and the valves will hang open.  With the valves slightly open carbon will start to build up on the face and seat, and if further neglected the valve will burn and crack.  

Depending on the maintenance history of your bikes engine it's possible for carbon to have accumulated on the sealing surfaces as TexasKZ mentioned.  If that's the case at least some of the carbon will wear off with more miles after adjustment.

We don't know the history of your bike so please take this information for how it's intended.

BTW, on my 750 the valve seats were very poorly machined from the factory; the margin varied around the seat, thin on one side and thick on the other.  It could be that your head just needs a valve job.  Hopefully not but just say'n...

Thanks for the reply. I posted a bit ago about how I went to do a valve adjustment and when I opened the valve cover discovered that someone had been in there and put the cams in flopped. So I put them back in the right way checked clearance and adjusted according to clearance specs. Started it and had number 4 cylinder be dead. Checked comp and found 0 pressure for that cylinder. Pulled the plug after checking piston was TDC and valves fully closed, no lobes on them, and did the quick leak down...and like wind through a tunnel out the carb! So either bent valve or as you said carbon. But my suspect is bent valve since the cams were flopped. anyways, head has to come off.

Oh, and its a low mileage 750...14,000 miles, so im hoping its just a bent valve on number 4. The bike ran on the other 3 cylinders so I dont think any other valves were damaged...fingers crossed

Do you have access to a borescope??

Bummer.  Be sure to buy OEM gaskets.  You can find good deals on ebay.  And change the valve stem seals while the head is off.   A member here sells Viton seals for good prices.  They are one of the few non-OEM parts that are better than stock.  Oh, and when pulling the head it's advises to pull the cylinder too and replace the base gasket.  

Good luck

Just asking out of curiosity...
If the valve is bent and hanging open, the clearance on the valve lash would have been larger than normal before you did any adjustments. Was that the case?
Also, you would then have had to swap in a larger shim than what was in there in order to get the reported .018 clearance, correct?

Bent valve

Its very easy to bend some valves when resetting the cams in on a GPZ750 style motor as that motor seems to have tight piston to valve pocket clearance, tighter than a KZ750 or KZ650 motor.

I am use to working with KZ650 motors and regular roller cam chain, you can be one tooth off either way and the valves will not hit even on high mileage motors.

On the 750 Spectre motor I have (it has same pistons as GPZ750) if your one tooth out it will bend a valve or two (did that myself last year)

It seems that even if the cam chain is within FSM wear specs on a engine with as little miles as your motor had on it, the timing marks on the advancer unit will not allow the cam sprocket marks to line up with the cylinder head faces as shown in the FSM thus causing misalignment and possible valve train damage (it says that in the FSM)

The other factor working against this alignment is that piss poor cam chain tensioner that the Hyvo motors have on them. You really need to make sure it is functioning properly before attempting to align the timing marks. Mine was all bound up and I did not realize it till after I did a leak down test.

I bent two valves slightly (one .004" and one .006") but was able to straighten them and regrind the faces. Not quite sure that valve you showed there can be saved, that is really bent!

What I did to elevate this situation (was not about to split the cases to mount a new cam chain) was to modify the cam chain tensioner to work like a manual unit, only with the spring still in there (drill thru for a bolt out the back) that helped a lot. I also ignored the timing marks and set the lobes by eye so that I knew the valves were closed at TDC. To verify I did a leak down test to make sure everything was sealing at TDC. This got my motor running correctly and just as good as the marks, but takes quite a bit longer.